Couplings have long been used for releasably interconnecting sections of tubular goods, such as industrial or fire hose, in fluid-tight engagement. Popular techniques for releasably connecting the faces of coupling bodies include cam action locking levers and variations of familiar male/female threaded joint couplings. Typically, these coupling bodies have compression seals with radially planar sealing surfaces.
One disadvantage of these couplings is the difficulty often experienced in manually making up these couplings for fluid-tight engagement. This difficulty is commonly the result of the significant amount of axial force required to establish both a fluid-tight seal under low fluid pressure while simultaneously having a seal which can withstand higher fluid pressure.
Another disadvantage of many prior art couplings is the use of coupling bodies with separate male and female components, whereby only hose sections with an opposite coupling can be joined. In fire emergency situations, long sections of hose having a coupling half attached to each end, are often hurriedly laid out to form a hose network to be connected later. If a hose section end is not properly adjacent another appropriately mated hose section end, precious time is wasted in rearranging sections until a matching coupling is found.
In the case of threaded couplings, another disadvantage is that multiple rotations are often necessary to securely join the coupling thereby increasing the effort and time required. These exposed threads are often subject to damage by foreign substances clogging the threads, metal fatigue, cross-threading and other damage in the dilaterious environment of fire scenes and industrial or oilfield applications.
For these and other reasons manually tightened couplings of a "quick-connect" variety were developed in the art which could establish a fluid-tight seal between two radially planar sealing surfaces by means of a partial relative rotation of the couplings along a common longitudinal axis. Although various techniques are known to releasably connect the faces of coupling bodies, a particularly desirable design is disclosed in commonly assigned U.S. Pat. No. 4,643,459 to Carson. However, problems have been associated with such couplings of the quick-connect design.
For example, a manual coupling using the "Storz" type seal has an annular groove set in a radially planar sealing end of each coupling body. An elastomeric seal having a rounded protrusion at its base is forced into the groove and held in place by a hook which fits over the protrusion.
Although in usual operation this forms an adequate sealing mechanism, this sealing technique is not without its shortcomings. Under very high pressures, this seal of the prior art tends to fold back upon itself until the seal is so distorted as to free itself from the retaining hook and, under extreme conditions, completely extrude between the coupling bodies.
When the pressure inside the coupling is reduced, the seal cannot return to its original location beneath the retaining hook and the seal remains broken. In extreme cases the seal body will remain wedged between the faces of the coupling and the locking mechanism may not be released without excessive force.
A coupling which uses the Storz seal technique is expensive to manufacture due to the intricate notch and groove arrangement of the sealing groove. Further, the Storz type seal is very difficult to install and remove without damaging the seal or taking an inordinate amount of time, particularly in the larger dimensions. In addition, these Storz type seals are unacceptable for food grade service because of the difficulty in removing and cleaning the seal and the inaccessible, hard to clean recesses caused by the hook and groove arrangement which provide sites for bacterial growth.
Another significant problem with a coupling having the Storz type seal is catastrophic failure in response to a pressure surge. If a coupling is pressured beyond its rated capacity (typical of the situation where a vehicle runs over the hose), the seal unseats itself from the retaining groove and begins to extrude through the space between the planar sealing surfaces of the coupling. Because of the nature of the seal and retaining hooks, the seal cannot reseat itself even after the pressure is reduced. Accordingly, the coupling will thereafter continue to leak with pressurized fluid spraying from the coupling. This failure mode, termed "catastrophic failure", makes couplings using the Storz type seals unsatisfactory for the transport of many liquids.
More exotic face seals are available which contain dual material, elastomeric seals which perform well in many applications. However, these dual material seals are expensive and require too much radial force on the coupling to energize the elastomer-to-elastomer seal for manual, quick-connect couplings.
These and other disadvantages are overcome by the invention hereinafter described wherein a novel coupling is disclosed.